Method for operating an oxygen sensor, computer program product and oxygen sensor

Abstract

A method and apparatus for compensates for oxygen sensor aging determines a correction of by measuring oxygen content above a specified threshold value and measuring current flowing through the sensor over time.

What is claimed is: 
     
       1. A method for operating an exhaust gas recirculation system having an oxygen sensor element for an intake tract of an internal combustion engine, wherein oxygen sensor element aging is compensated for as a function of oxygen sensor element operating time, the method comprising;
 providing a first amount of exhaust gas from the internal combustion engine into the intake tract and providing ambient air into the intake tract to provide a gaseous mixture of exhaust gas and ambient air to the oxygen sensor element; 
 measuring a pumping current required to pump oxygen that is in the gaseous mixture of exhaust gas and ambient air, through a zirconium membrane of the oxygen sensor element; 
 determining oxygen content in the gaseous mixture of exhaust gas and ambient air by evaluating the equation:
   O 2   =r *( a+b*I   pump   +c*I   pump   2 ), 
 
 
       wherein I pump  is the measured pumping current, a, b and c are factors for quadratic factory calibration, and r is a recalibration factor for aging compensation;
 changing the value of r, responsive to the operating time of the oxygen sensor element; 
 and 
 changing the first amount of exhaust gas provided into the intake tract responsive to an oxygen content determined by the oxygen sensor element to be in the gaseous mixture of exhaust gas and ambient air, after the value of r is changed. 
 
     
     
       2. The method of  claim 1 , wherein the aging compensation is performed responsive to determining a contamination of the sensor element. 
     
     
       3. The method of  claim 1 , wherein the aging compensation is performed at fixed operating time intervals, the fixed operating time intervals being determined responsive to the operating time of the sensor element. 
     
     
       4. The method of  claim 1 , wherein oxygen content of ambient air is used as a threshold value. 
     
     
       5. The method of  claim 1 , wherein correction of the aging compensation is performed when the oxygen sensor delivers, over a specified time period, at least a specified number of measured values of oxygen content above the specified threshold value. 
     
     
       6. A computer having a computer-readable medium and program code stored in the computer-readable medium, which, when executed causes the computer to execute a method as claimed in  claim 1 . 
     
     
       7. An apparatus comprising:
 an internal combustion engine having an exhaust gas recirculation system comprising an air intake tract, an exhaust tract and an exhaust gas recirculation pipe coupled between the air intake tract and the exhaust tract, the exhaust gas recirculation system being configured to combine engine exhaust gas with ambient air to provide a mixture of exhaust gas and ambient air to the internal combustion engine, the amount of exhaust gas added into the ambient air being determined responsive to a measured level of oxygen in the gaseous mixture; 
 an oxygen sensor in the gaseous mixture, the oxygen sensor comprising yttrium-stabilized zirconium oxide ceramic; 
 a computer, operatively coupled to the oxygen sensor; 
 a memory device operatively coupled to the computer and storing program instructions, which when executed cause the computer to: 
 compensate for aging of the oxygen sensor as a function of an operating time of the oxygen sensor; 
 the compensation comprising:
 measuring a pumping current required to pump oxygen through a zirconium membrane of the sensor; 
 determining oxygen content by evaluating the equation:
   O 2   =r *( a+b*I   pump   +c*I   pump   2 ), 
 
  wherein I pump  is the measured pumping current, a, b and c are factors for quadratic factory calibration, and r is a recalibration factor for aging compensation; 
 changing the value of r, responsive to the operating time of the sensor element; 
 
 and 
 wherein the apparatus is configured to change the amount of engine exhaust gas provided to the ambient air responsive to an oxygen content that is determined, after the oxygen sensor aging is compensated for.